AC Installation in Hermann, MO

Which first-time central air installation fits your house?

This page covers new air conditioning where none exists today. If a central system is already in place and has failed or aged out, our AC replacement page is the one you want. For a first system, your starting point decides most of the scope.

The U.S. Department of Energy describes central air as the most even cooling for a home, and also warns it can be expensive to install without ductwork already in place. If you have no furnace either, price a heat pump alongside it, because one outdoor unit can then handle both seasons.

AC system sizing: what the load calculation settles

Size the system with an ACCA Manual J load calculation, never by square footage. An analysis of 40 Manual J calculations on ACCA's blog ran from 624 to 3,325 square feet per ton, and every one came in above the 400 to 600 rule of thumb still quoted in the trade.

Oversizing costs you comfort here. PNNL's Building America guidance explains that an oversized unit reaches the thermostat setting before moisture can condense on the coil, so the house cools while humidity climbs. In the river valley, that is the difference between comfortable and clammy.

Ducts come next

ACCA Manual D sizes the ducts, and Manual S guides equipment selection, with cooling capacity up to 15% over the calculated load. On a house with heating ducts, we check whether the trunk and returns can carry cooling airflow. The Department of Energy's advice is simple: ducts should be sealed and connected without sags or excessive bends.

Power, drainage and placement

A first system needs a dedicated circuit, room in the panel, a condensate route and a level spot for the outdoor unit. Natural Resources Canada advises keeping refrigerant lines as short as possible. On new construction it also suggests a frame on the house, so the unit stays level as backfill settles.

What is included in an AC installation

Ask any contractor to put these items in writing. Our quote names the scope before we start.

• A Manual J load calculation for the house as it is, or as drawn
• Equipment selection: outdoor unit, matched indoor coil or air handler, and thermostat
• A duct plan, covering new runs, changes to existing ducts and return air
• Refrigerant lines, with the wall opening sealed against air and noise
• The electrical feed and outdoor disconnect
• A condensate drain, routed so overflow cannot reach a finished ceiling
• Startup, refrigerant charge and airflow checks, with a walk-through of filter and thermostat

How a first-time install runs, step by step

1. We walk the house or review the plans, and measure what the load calculation needs.
2. We run the load, choose the equipment and lay out the duct routes.
3. You get a clear, upfront quote, and we settle who pulls the mechanical permit.
4. Ductwork goes in first. On a new build that is the rough-in, before insulation and drywall.
5. We set the indoor coil or air handler, and then the outdoor unit on its pad.
6. We run the lines, connect power and the drain, and pressure-test the refrigerant circuit.
7. We evacuate the lines, charge the system and start it.
8. We measure airflow and temperature split, then show you the filter and thermostat.

The duct work sets the calendar. A furnace-and-ducts house has far less to build than a house with none, so we give you the schedule with the quote. Builders should expect two visits, one at rough-in and one at finish.

How much does central air cost to add?

Existing ductwork is the biggest factor. PickHVAC's 2025 national guide puts installation at $2,500 to $7,500 with ducts in place and $6,000 to $12,000 with new ductwork. These are outside figures, not our prices, so ask us for a quote on your house.

Five things move the number:

• Ductwork: none, partial or a full new system
• Size and efficiency: the tonnage from your load calculation, and the SEER2 rating you choose
• Electrical: a new circuit, or panel work on an older service
• Access: tight attics, finished basements and long line runs
• Furnace condition: an old blower or cabinet may not suit a new coil

There is no federal credit to count on for a 2026 install, since 25C stopped covering equipment placed in service after December 31, 2025. Missouri has no state credit either. Check with your tax adviser.

Permits and refrigerant rules for new systems

Missouri has no statewide HVAC contractor license as of late 2026, so permits and contractor rules are set city by city and county by county. Ask city hall or the county what applies at your address, and ask who pulls the mechanical permit.

Federal rules still apply. The EPA requires new split systems installed after January 1, 2026 to use refrigerant with a global warming potential below 700. The federal minimum for a split-system AC in the North region, which includes Missouri, is 13.4 SEER2 under 45,000 Btu/h.

Why Brian Grannemann Services for a first central air system

• New construction is listed among our trades on Google, alongside heating and cooling, so a builder's schedule is familiar ground.
• Electrical and plumbing are on that list too, which helps when a new system needs a circuit or a drain route.
• We have been in business since 1998 and keep an office at 124 E 10th St, so you can sit down with the plans.
• Stephanie H. wrote that Brian "consistently shows up when promised, completes the work correctly the first time." That counts on a build with other trades waiting.

Caring for a new system, and where we install

Check the filter monthly through the first summer, because new construction dust loads it quickly. Keep the outdoor unit clear of mulch and shrubs, then book a spring AC tune-up from the second year on.

Call (209) 563-1270 with your plans or your address. We plan first-time systems from Hermann across the region, including Washington, New Haven, Warrenton and Union.